1. Field of the Invention
The present invention relates to a setting solution for calcium phosphate cement and to a calcium phosphate cement composition containing the setting solution. The setting solution and the composition of the present invention are useful in the medical and dental fields. Particularly, the composition containing the setting solution and calcium phosphate cement of the invention is advantageously used to form, for example, artificial bone, artificial tooth roots, and artificial joints which have both excellent strength and excellent compatibility with living tissue.
2. Description of the Related Art
Numerous different compositions of medical cement used for the living body have so far been proposed. Among such compositions, biocompatible cement of the calcium phosphate type yields hard material of excellent biotropism, since the cement powder transforms into hydroxyapatite as the powder sets.
After being kneaded, a conventional mixture of calcium phosphate-type biocompatible cement and pure water sets in 10-20 minutes in air. However, when the mixture is immediately immersed in water after being kneaded, powder disperses into the water before the mixture is set, causing the mass of cement to disintegrate. Therefore, in the case in which such a biocompatible cement is placed in the living body--which contains large amounts of body fluid--some countermeasures must be taken. For example, a kneaded mixture may be allowed to set to a certain degree before being put in the living body. Alternatively, the body fluid present in the location receiving the cement is first removed, then hemostasis and other similar treatment is performed, and subsequently the kneaded material is placed in the body.
However, cement which is set to a certain degree is difficult to handle and may cause incorrect shaping. Moreover, removal of body fluid and hemostasis require human hands and time. To solve these problems, there has been proposed a preparation containing a cement powder and a specified setting solution. For example, U.S. Pat. No. 4,612,053 discloses the addition of acid to a setting solution to shorten the setting time and thereby reduce the extent of disintegration. Japanese Patent Application No. 77261/1990 discloses addition of chitosan to a setting solution to further suppress dispersion of powder and disintegration of the cement. However, if a cement and a setting solution containing an acid is placed in the living body, the acid irritates the skin considerably and can cause an inflammatory reaction in the vicinity of the filled portion. In addition, in order to dissolve chitosan, the pH of the aqueous solution must be adjusted to 1-2, which as a matter of course requires addition of an acid, raising the inflammation problem again.